/*
 Copyright  2002-2007 MySQL AB, 2008 Sun Microsystems
 All rights reserved. Use is subject to license terms.

  The MySQL Connector/J is licensed under the terms of the GPL,
  like most MySQL Connectors. There are special exceptions to the
  terms and conditions of the GPL as it is applied to this software,
  see the FLOSS License Exception available on mysql.com.

  This program is free software; you can redistribute it and/or
  modify it under the terms of the GNU General Public License as
  published by the Free Software Foundation; version 2 of the
  License.

  This program is distributed in the hope that it will be useful,  
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  02110-1301 USA



 */
package com.mysql.jdbc;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.SQLException;

/**
 * The representation (mapping) in the JavaTM programming language of an SQL
 * BLOB value. An SQL BLOB is a built-in type that stores a Binary Large Object
 * as a column value in a row of a database table. The driver implements Blob
 * using an SQL locator(BLOB), which means that a Blob object contains a logical
 * pointer to the SQL BLOB data rather than the data itself. A Blob object is
 * valid for the duration of the transaction in which is was created. Methods in
 * the interfaces ResultSet, CallableStatement, and PreparedStatement, such as
 * getBlob and setBlob allow a programmer to access an SQL BLOB value. The Blob
 * interface provides methods for getting the length of an SQL BLOB (Binary
 * Large Object) value, for materializing a BLOB value on the client, and for
 * determining the position of a pattern of bytes within a BLOB value. This
 * class is new in the JDBC 2.0 API.
 * 
 * @author Mark Matthews
 * @version $Id$
 */
public class Blob implements java.sql.Blob, OutputStreamWatcher {

	//
	// This is a real brain-dead implementation of BLOB. Once I add
	// streamability to the I/O for MySQL this will be more efficiently
	// implemented (except for the position() method, ugh).
	//

	/** The binary data that makes up this BLOB */
	private byte[] binaryData = null;
	private boolean isClosed = false;
	private ExceptionInterceptor exceptionInterceptor;
	
	/**
     * Creates a Blob without data
     */
    Blob(ExceptionInterceptor exceptionInterceptor) {
        setBinaryData(Constants.EMPTY_BYTE_ARRAY);
        this.exceptionInterceptor = exceptionInterceptor;
    }
    
	/**
	 * Creates a BLOB encapsulating the given binary data
	 * 
	 * @param data
	 *            DOCUMENT ME!
	 */
	Blob(byte[] data, ExceptionInterceptor exceptionInterceptor) {
		setBinaryData(data);
		this.exceptionInterceptor = exceptionInterceptor;
	}

	/**
	 * Creates an updatable BLOB that can update in-place (not implemented yet).
	 * 
	 * @param data
	 *            DOCUMENT ME!
	 * @param creatorResultSetToSet
	 *            DOCUMENT ME!
	 * @param columnIndexToSet
	 *            DOCUMENT ME!
	 */
	Blob(byte[] data, ResultSetInternalMethods creatorResultSetToSet, int columnIndexToSet) {
		setBinaryData(data);
	}

	private synchronized byte[] getBinaryData() {
		return this.binaryData;
	}

	/**
	 * Retrieves the BLOB designated by this Blob instance as a stream.
	 * 
	 * @return this BLOB represented as a binary stream of bytes.
	 * 
	 * @throws SQLException
	 *             if a database error occurs
	 */
	public synchronized java.io.InputStream getBinaryStream() throws SQLException {
		checkClosed();
		
		return new ByteArrayInputStream(getBinaryData());
	}

	/**
	 * Returns as an array of bytes, part or all of the BLOB value that this
	 * Blob object designates.
	 * 
	 * @param pos
	 *            where to start the part of the BLOB
	 * @param length
	 *            the length of the part of the BLOB you want returned.
	 * 
	 * @return the bytes stored in the blob starting at position
	 *         <code>pos</code> and having a length of <code>length</code>.
	 * 
	 * @throws SQLException
	 *             if a database error occurs
	 */
	public synchronized byte[] getBytes(long pos, int length) throws SQLException {
		checkClosed();
		
		if (pos < 1) {
			throw SQLError.createSQLException(Messages.getString("Blob.2"), //$NON-NLS-1$
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}

		pos--;
		
		if (pos > this.binaryData.length) {
			throw SQLError.createSQLException("\"pos\" argument can not be larger than the BLOB's length.", 
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}
		
		if (pos + length > this.binaryData.length) {
			throw SQLError.createSQLException("\"pos\" + \"length\" arguments can not be larger than the BLOB's length.", 
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}
		
		byte[] newData = new byte[length];
		System.arraycopy(getBinaryData(), (int) (pos), newData, 0, length);

		return newData;
	}

	/**
	 * Returns the number of bytes in the BLOB value designated by this Blob
	 * object.
	 * 
	 * @return the length of this blob
	 * 
	 * @throws SQLException
	 *             if a database error occurs
	 */
	public synchronized long length() throws SQLException {
		checkClosed();
		
		return getBinaryData().length;
	}

	/**
	 * @see java.sql.Blob#position(byte[], long)
	 */
	public synchronized long position(byte[] pattern, long start) throws SQLException {
		throw SQLError.createSQLException("Not implemented", this.exceptionInterceptor); //$NON-NLS-1$
	}

	/**
	 * Finds the position of the given pattern in this BLOB.
	 * 
	 * @param pattern
	 *            the pattern to find
	 * @param start
	 *            where to start finding the pattern
	 * 
	 * @return the position where the pattern is found in the BLOB, -1 if not
	 *         found
	 * 
	 * @throws SQLException
	 *             if a database error occurs
	 */
	public synchronized long position(java.sql.Blob pattern, long start) throws SQLException {
		checkClosed();
		
		return position(pattern.getBytes(0, (int) pattern.length()), start);
	}

	private synchronized void setBinaryData(byte[] newBinaryData) {
		this.binaryData = newBinaryData;
	}

	/**
	 * @see Blob#setBinaryStream(long)
	 */
	public synchronized OutputStream setBinaryStream(long indexToWriteAt)
			throws SQLException {
		checkClosed();
		
		if (indexToWriteAt < 1) {
			throw SQLError.createSQLException(Messages.getString("Blob.0"), //$NON-NLS-1$
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}

		WatchableOutputStream bytesOut = new WatchableOutputStream();
		bytesOut.setWatcher(this);

		if (indexToWriteAt > 0) {
			bytesOut.write(this.binaryData, 0, (int) (indexToWriteAt - 1));
		}

		return bytesOut;
	}

	/**
	 * @see Blob#setBytes(long, byte[])
	 */
	public synchronized int setBytes(long writeAt, byte[] bytes) throws SQLException {
		checkClosed();
		
		return setBytes(writeAt, bytes, 0, bytes.length);
	}

	/**
	 * @see Blob#setBytes(long, byte[], int, int)
	 */
	public synchronized int setBytes(long writeAt, byte[] bytes, int offset, int length)
			throws SQLException {
		checkClosed();
		
		OutputStream bytesOut = setBinaryStream(writeAt);

		try {
			bytesOut.write(bytes, offset, length);
		} catch (IOException ioEx) {
			SQLException sqlEx = SQLError.createSQLException(Messages.getString("Blob.1"), //$NON-NLS-1$
					SQLError.SQL_STATE_GENERAL_ERROR, this.exceptionInterceptor);
			sqlEx.initCause(ioEx);
			
			throw sqlEx;
		} finally {
			try {
				bytesOut.close();
			} catch (IOException doNothing) {
				; // do nothing
			}
		}

		return length;
	}

	/**
	 * @see com.mysql.jdbc.OutputStreamWatcher#streamClosed(byte[])
	 */
	public synchronized void streamClosed(byte[] byteData) {
		this.binaryData = byteData;
	}

	/**
	 * @see com.mysql.jdbc.OutputStreamWatcher#streamClosed(byte[])
	 */
	public synchronized void streamClosed(WatchableOutputStream out) {
		int streamSize = out.size();

		if (streamSize < this.binaryData.length) {
			out.write(this.binaryData, streamSize, this.binaryData.length
					- streamSize);
		}

		this.binaryData = out.toByteArray();
	}

	/**
     * Truncates the <code>BLOB</code> value that this <code>Blob</code>
     * object represents to be <code>len</code> bytes in length.
     * <p>
     * <b>Note:</b> If the value specified for <code>len</code>
     * is greater then the length+1 of the <code>BLOB</code> value then the 
     * behavior is undefined. Some JDBC drivers may throw a 
     * <code>SQLException</code> while other drivers may support this 
     * operation.
     *
     * @param len the length, in bytes, to which the <code>BLOB</code> value
     *        that this <code>Blob</code> object represents should be truncated
     * @exception SQLException if there is an error accessing the
     *            <code>BLOB</code> value or if len is less than 0
     * @exception SQLFeatureNotSupportedException if the JDBC driver does not support
     * this method
     * @since 1.4
     */
	//截取原字节数组的前len个字节，然后把得到的新数组赋给原数组
	public synchronized void truncate(long len) throws SQLException {
		checkClosed();
		
		if (len < 0) {
			throw SQLError.createSQLException("\"len\" argument can not be < 1.", 
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}
		
		if (len > this.binaryData.length) {
			throw SQLError.createSQLException("\"len\" argument can not be larger than the BLOB's length.", 
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}
		
		// TODO: Do this without copying byte[]s by maintaining some end pointer
		// on the original data
		
		byte[] newData = new byte[(int)len];
		System.arraycopy(getBinaryData(), 0, newData, 0, (int)len);
		this.binaryData = newData;
	}

	/**
     * This method frees the <code>Blob</code> object and releases the resources that 
     * it holds. The object is invalid once the <code>free</code>
     * method is called.
     *<p>
     * After <code>free</code> has been called, any attempt to invoke a
     * method other than <code>free</code> will result in a <code>SQLException</code> 
     * being thrown.  If <code>free</code> is called multiple times, the subsequent
     * calls to <code>free</code> are treated as a no-op.
     *<p>
     * 
     * @throws SQLException if an error occurs releasing
     * the Blob's resources
     * @exception SQLFeatureNotSupportedException if the JDBC driver does not support
     * this method
     * @since 1.6
     */
	
	public synchronized void free() throws SQLException {
		this.binaryData = null;
		this.isClosed = true;
	}

	/**
     * Returns an <code>InputStream</code> object that contains a partial <code>Blob</code> value, 
     * starting  with the byte specified by pos, which is length bytes in length.
     *
     * @param pos the offset to the first byte of the partial value to be retrieved.
     *  The first byte in the <code>Blob</code> is at position 1
     * @param length the length in bytes of the partial value to be retrieved
     * @return <code>InputStream</code> through which the partial <code>Blob</code> value can be read.
     * @throws SQLException if pos is less than 1 or if pos is greater than the number of bytes
     * in the <code>Blob</code> or if pos + length is greater than the number of bytes 
     * in the <code>Blob</code>
     *
     * @exception SQLFeatureNotSupportedException if the JDBC driver does not support
     * this method
     * @since 1.6
     */
	public synchronized InputStream getBinaryStream(long pos, long length) throws SQLException {
		checkClosed();
		
		if (pos < 1) {
			throw SQLError.createSQLException("\"pos\" argument can not be < 1.", 
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}
		
		pos--;
		
		if (pos > this.binaryData.length) {
			throw SQLError.createSQLException("\"pos\" argument can not be larger than the BLOB's length.", 
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}
		
		if (pos + length > this.binaryData.length) {
			throw SQLError.createSQLException("\"pos\" + \"length\" arguments can not be larger than the BLOB's length.", 
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}
		
		return new ByteArrayInputStream(getBinaryData(), (int)pos, (int)length);
	}
	
	private synchronized void checkClosed() throws SQLException {
		if (this.isClosed) {
			throw SQLError.createSQLException("Invalid operation on closed BLOB", 
					SQLError.SQL_STATE_ILLEGAL_ARGUMENT, this.exceptionInterceptor);
		}
	}
}
